Lecture 4 Chapter 1: Roadmap 1.1 what is the Internet? 1.2 network edge end systems, access networks, links 1.3 network core packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history 1-2 1
Internet history 1961-1972: Early packet-switching principles 1961: Kleinrock 1972: queueing theory shows ARPAnet public demo effectiveness of packetswitching NCP (Network Control Protocol) first host host 1964: Baran packetswitching in military nets protocol 1967: ARPAnet first e mail program conceived by Advanced ARPAnet has 15 nodes Research Projects Agency 1969: first ARPAnet node operational 1-3 Internet history 1972-1980: Internetworking, new and proprietary nets 1970: ALOHAnet satellite network in Hawaii 1974: Cerf and Kahn architecture for interconnecting networks 1976: Ethernet at Xerox PARC late70 s: proprietary architectures: DECnet, SNA, XNA late 70 s: switching fixed length packets (ATM precursor) 1979: ARPAnet has 200 nodes Cerf and Kahn s internetworking principles: minimalism, autonomy no internal changes required to interconnect networks best effort service model stateless routers decentralized control define today s Internet architecture 1-4 2
1983: deployment of TCP/IP 1982: smtp e mail protocol defined 1983: DNS defined for name to IP address translation 1985: ftp protocol defined 1988: TCP congestion control Internet history 1980-1990: new protocols, a proliferation of networks new national networks: Csnet, BITnet, NSFnet, Minitel 100,000 hosts connected to confederation of networks 1-5 Internet history 1990, 2000 s: commercialization, the Web, new apps early 1990 s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) early 1990s: Web hypertext [Bush 1945, Nelson 1960 s] HTML, HTTP: Berners Lee 1994: Mosaic, later Netscape late 1990 s: commercialization of the Web late 1990 s 2000 s: more killer apps: instant messaging, P2P file sharing network security to forefront est. 50 million host, 100 million+ users backbone links running at Gbps 1-6 3
Internet history 2005 present ~750 million hosts Smartphones and tablets Aggressive deployment of broadband access Increasing ubiquity of high speed wireless access Emergence of online social networks: Facebook: soon one billion users Service providers (Google, Microsoft) create their own networks Bypass Internet, providing instantaneous access to search, emai, etc. E commerce, universities, enterprises running their services in cloud (eg, Amazon EC2) 1-7 Internet Statistics 2.1 billion Internet users 35 billion hours/month spent on Internet = 3,995,444 years/month 835 million active Facebook users (March 2012, http://www.internetworldstats.com/facebook.htm) 500 million active Twitter users (http://en.wikipedia.org/wiki/twitter) 175 million active LinkedIn users (August 2012, http://press.linkedin.com/about) 4 billion users/day at YouTube 1 billion queries per day at Google 800 million updates/day at Facebook 340 million Tweets/day at Twitter (March 2012, http://en.wikipedia.org/wiki/twitter) 60 hours of video uploads every minute at YouTube Unique visits/month 153,441,000 Google 137,644,000 Facebook 130,121,000 Yahoo 115,890,000 MSN Bing 106,692,000 You Tube http://www.mediabistro.com/alltwitter/online time_b22186 (May 2012) http://www.mediabistro.com/alltwitter/twitter 140 million active users_b19729 4
Internet Statistics Websites Name Description/Focus Date launched Registered users Registration Facebook General: Photos, Videos, Blogs, Apps. February 2004 908,000,000 Open to people 13 and older Twitter General. Micro blogging, RSS, updates July 15, 2006 500,000,000 Open to all ages Qzone General. In Simplified Chinese; caters for mainland China users 480,000,000 Open to the general public Sina Weibo Social microblogging site in Mainland China. August 14, 2009 300,000,000 Open Habbo General for teens. Over 31 communities worldwide. Chat room and user profiles. August 2000 268,000,000 Open to people 13 and older Google+ General June 28, 2011 250,000,000 Open to people 13 and older Renren Significant site in China. Was known as 校内 (Xiaonei) until August 2009. 160,000,000 Open LinkedIn Business and professional networking May 2003 160,000,000 Open to people 18 and older Badoo General, Meet new people & dating, Popular in Europe and Latin America January 2006 154,000,000 Open to people 18 and older Vkontakte General, including music upload, listening and search. Popular in Russia and former Soviet republics. September 2006 123,612,100 Open Bebo General July 2005 117,000,000 Open to people 13 and older Tagged General. October 2004 100,000,000 Open Orkut General. Owned by Google Inc. Popular in India and Brazil January 22, 2004 100,000,000 Open to people 18 and older, (Google login) http://en.wikipedia.org/wiki/list_of_social_networking_websites Introduction: summary covered a ton of material! Internet overview what s a protocol? network edge, core, access network packet switching versus circuit switching Internet structure performance: loss, delay, throughput layering, service models security history you now have: context, overview, feel of networking more depth, detail to follow! 1-10 5
Chapter 2 Application Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) that you mention their source (after all, we d like people to use our book!) If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Thanks and enjoy! JFK/KWR Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 All material copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved 2-11 Chapter 2: Outline 2.1 principles of network applications 2.2 Web and HTTP 2.3 FTP 2.4 electronic mail SMTP, POP3, IMAP 2.5 DNS 2.6 P2P applications 2.7 socket programming with UDP and TCP 2-12 6
Chapter 2: Application layer our goals: conceptual, implementation aspects of network application protocols transport layer service models client server paradigm peer to peer paradigm learn about protocols by examining popular application level protocols HTTP FTP SMTP / POP3 / IMAP DNS creating network applications socket API 2-13 Some network apps e mail web text messaging remote login P2P file sharing multi user network games streaming stored video (YouTube, Hulu, Netflix) voice over IP (e.g., Skype) real time video conferencing social networking search 2-14 7
e mail and Messaging Statistics e mail 2.2 billion users 247 billion emails are sent each day http://www.radicati.com/wp/wp content/uploads/2012/04/email Statistics Report 2012 2016 Brochure.pdf Key Global Telecom Indicators for the World (estimates) Over-the-Top (OTT) messaging v SMS messaging. OTT messages SMS MMS messages messages 2011 3,492 billion 7,844 billion 207 billion 2012 5,846 billion 8,600 billion 228 billion 2016 20,293 billion 9,554 billion 277 billion Sources: Portio Research Febuary 2012 Global millions Per 100 people Mobile cellular subscriptions 5,981 86.7 Fixed telephone lines 1,159 16.6 Active mobile broadband subscriptions 1,186 17.0 Fixed broadband subscriptions 591 8.5 Source: International Telecommunication Union (November 2011) via: mobi Thinking http://mobithinking.com/mobile marketing tools/latest mobilestats/c#mobilemessaging Video on the Internet Top 10 U.S. Online Video Content Properties Ranked by Unique Video Viewers, March 2012 Total U.S. Home and Work Locations Content Videos Only (Ad Videos Not Included) Source: comscore Video Metrix Property Total Unique Viewers (000) Videos (000)* Minutes per Viewer Total Internet : Total Audience 181,062 36,984,872 1,304.8 Google Sites 146,097 15,748,884 424.6 Yahoo! Sites 60,609 814,838 72.4 VEVO 51,337 706,291 63.0 Facebook 45,073 247,010 21.3 Viacom Digital 44,251 547,732 63.2 AOL, Inc. 43,701 496,415 50.3 Turner Digital 42,917 288,887 24.8 Microsoft Sites 41,169 494,529 46.7 Comcast NBCUniversal 32,164 178,189 36.9 Hulu 31,104 1,010,527 275.2 *A video is defined as any streamed segment of audiovisual content, including both progressive downloads and live streams. For long-form, segmented content, (e.g. television episodes with ad pods in the middle) each segment of the content is counted as a distinct video stream. http://www.comscore.com/press_events/press_releases/2012/4/comscore_releases_march_2012_u.s._online_video_rankings 8
Internet Traffic Forecast Internet highlights In 2016 global IP traffic will reach 1.3 ZB/year or 110.3 EB/month, a compound annual growth rate (CAGR) of 29% from 2011. In 2016, the GB equivalent of all movies ever made will cross global IP networks every 3 minutes delivering 12.5 ZB every 5 minutes. There will be nearly three networked devices per capita in 2016, up from over one networked device per capita in 2011. IP traffic per capita will reach 15 GB/capita in 2016, up from 4 GB/capita in 2011. In 2016 non PC originated IP traffic will account for 31% of all IP traffic, up from 22% in 2011. In 2016 the non PC consumer internet traffic will account for 20% of the consumer internet traffic, up from 6% in 2011. PC originated traffic will grow at a CAGR of 28%, while TVs, tablets, smartphones, and business Internet machine to machine (M2M) modules will have growth rates of 42%, 116%, 119%, and 86%, respectively. In 2016, wired devices will account for 39% of IP traffic, while Wi Fi and mobile devices will account for 61%. In 2011, wired devices accounted for 55%. Busy hour IP traffic will increase nearly 5 fold by 2016, while average traffic will increase nearly 4 fold. Busy hour Internet traffic will reach 720 Tbps in 2016, the equivalent of 600 million people streaming Internet high definition video simultaneously. Video Highlights It would take over 6 million years to watch the amount of video that will cross global IP networks each month in 2016. Every second, 1.2 million minutes of video content will cross the network. Globally, in 2016 Internet video traffic will be 55% of all consumer Internet traffic, up from 51% in 2011 excluding video exchanged through peer to peer (P2P) file sharing. Video exceeded half of global consumer Internet traffic by year end 2011. The sum of all forms of video (TV, video on demand [VoD], Internet, and P2P) will be approximately 86% of global consumer traffic by 2016. Internet video to TV will increase 6 fold by 2016 accounting for 12% of consumer Internet video traffic, up from 8% in 2011. Video on demand traffic will triple by 2016 to an amount equivalent to 4 billion DVDs per month. High definition VoD surpassed standard definition by the end of 2011. By 2016, high definition Internet video will comprise 79% of VoD. Mobile Highlights Globally, mobile data traffic will increase 18 fold between 2011 and 2016 (a CAGR of 78%), reaching 10.8 EB/month by 2016. Global mobile data traffic will grow three times faster than fixed IP traffic from 2011 to 2016 from 2% to 10% of total IP traffic in 2016. Remark: Past forecasts have been accurate to within about 5%. http://www.cisco.com/en/us/solutions/collateral/ns341/ns525/ns537/ns705/ns827/white_paper_c11 481360_ns827_Networking_Solutions_White_Paper.html Creating a network app write programs that: run on (different) end systems communicate over network e.g., web server software communicates with browser software no need to write software for network core devices network core devices do not run user applications applications on end systems allows for rapid app development, propagation application transport network data link physical application transport network data link physical application transport network data link physical 2-18 9
Application architectures possible structure of applications: client server peer to peer (P2P) 2-19 Client server architecture server: always on host permanent IP address data centers for scaling client/server clients: communicate with server may be intermittently connected may have dynamic IP addresses do not communicate directly with each other 2-20 10
no always on server arbitrary end systems directly communicate peers request service from other peers, provide service in return to other peers self scalability new peers bring new service capacity, as well as new service demands peers are intermittently connected and change IP addresses complex management P2P architecture peer-peer 2-21 A P2P Application example: Bit Torrent BitTorrent is a peer to peer file sharing protocol in which files being distributed are divided into pieces. As each peer receives a new piece it becomes a source (of that piece) for other peers, relieving the original seed from having to send that piece to every computer or user wishing a copy. The task of distributing the file is shared by those who want it; it is entirely possible for the seed to send only a single copy of the file itself and eventually distribute to an unlimited number of peers. Peer to peer networks collectively are estimated to account for 43% to 70% of all Internet traffic (depending on geographical location) as of February 2009. As of January 2012, BitTorrent has 150 million active users according to BitTorrent, Inc with an estimated more than a quarter billion monthly users. At any given instant BitTorrent has, on average, more active users than YouTube and Facebook combined. (This refers to the number of active users at any instant and not to the total number of unique users.) In 2008, the CBC became the first public broadcaster in North America to make a full show available for download using BitTorrent. The Amazon S3 "Simple Storage Service" is a scalable Internet based storage service with a simple web service interface, equipped with built in BitTorrent support. http://en.wikipedia.org/wiki/bittorrent_(protocol) 11
Processes communicating process: program running within a host within same host, two processes communicate using inter process communication (defined by OS) processes in different hosts communicate by exchanging messages clients, servers client process: process that initiates communication server process: process that waits to be contacted aside: applications with P2P architectures have client processes & server processes 2-23 Sockets process sends/receives messages to/from its socket socket analogous to door sending process shoves message out door sending process relies on transport infrastructure on other side of door to deliver message to socket at receiving process application process socket application process controlled by app developer transport network link physical Internet transport network link physical controlled by OS 2-24 12
Addressing processes to receive messages, process must have identifier host device has unique 32 bit IP address Q: does IP address of host on which process runs suffice for identifying the process? A: no, many processes can be running on same host identifier includes both IP address and port numbers associated with process on host. example port numbers: HTTP server: 80 mail server: 25 to send HTTP message to gaia.cs.umass.edu web server: IP address: 128.119.245.12 port number: 80 more shortly 2-25 App layer protocol defines types of messages exchanged, e.g., request, response message syntax: what fields in messages & how fields are delineated message semantics meaning of information in fields rules for when and how processes send & respond to messages open protocols: defined in RFCs allows for interoperability e.g., HTTP, SMTP proprietary protocols: e.g., Skype 2-26 13
What transport service does an app need? data integrity some apps (e.g., file transfer, web transactions) require 100% reliable data transfer other apps (e.g., audio) can tolerate some loss timing some apps (e.g., Internet telephony, interactive games) require low delay to be effective throughput some apps (e.g., multimedia) require minimum amount of throughput to be effective other apps ( elastic apps ) make use of whatever throughput they get security encryption, data integrity, 2-27 Transport service requirements: common apps application data loss throughput time sensitive file transfer e-mail Web documents real-time audio/video stored audio/video interactive games text messaging no loss no loss no loss loss-tolerant loss-tolerant loss-tolerant no loss elastic elastic elastic audio: 5kbps-1Mbps video:10kbps-5mbps same as above few kbps up elastic no no no yes, 100 s msec yes, few secs yes, 100 s msec yes and no 2-28 14
Internet transport protocols services TCP service: reliable transport between sending and receiving process flow control: sender won t overwhelm receiver congestion control: throttle sender when network overloaded does not provide: timing, minimum throughput guarantee, security connection oriented: setup required between client and server processes UDP service: unreliable data transfer between sending and receiving process does not provide: reliability, flow control, congestion control, timing, throughput guarantee, security, orconnection setup, Q: why bother? Why is there a UDP? 2-29 Internet apps: application, transport protocols application e-mail remote terminal access Web file transfer streaming multimedia Internet telephony application layer protocol SMTP [RFC 2821] Telnet [RFC 854] HTTP [RFC 2616] FTP [RFC 959] HTTP (e.g., YouTube), RTP [RFC 1889] SIP, RTP, proprietary (e.g., Skype) underlying transport protocol TCP TCP TCP TCP TCP or UDP TCP or UDP 2-30 15
Securing TCP TCP & UDP no encryption cleartext passwds sent into socket traverse Internet in cleartext SSL provides encrypted TCP connection data integrity end point authentication SSL is at app layer Apps use SSL libraries, which talk to TCP SSL socket API cleartext passwds sent into socket traverse Internet encrypted See Chapter 7 2-31 16